The present invention relates to a moisture absorbing mechanism and a magnetic disk drive having the moisture absorbing mechanism.
There are two major technical tasks to be accomplished in the development of magnetic disk drives. One is achievement of a higher data transmission rate, and the other is achievement of a larger recording capacity of the magnetic disk drive. In order to achieve the larger recording capacity, a recording density of recording data on a magnetic disk is increased by reducing a flying height of a magnetic head. With the reduction in flying height of the magnetic head, a distance between the magnetic head and the magnetic disk is reduced, and a flying stability of the magnetic head becomes subject to disturbance. Also, if dew condensation occurs on the magnetic head, the flying of the magnetic head becomes unstable to cause contact of the magnetic head with the magnetic disk, thereby damaging the magnetic head and the magnetic disk as well as degrading their reliability. In the case of resulting in a crush, information on the magnetic disk can be lost. Further, the magnetic head and the magnetic disk can be corroded due to the occurrence of dew condensation, thereby degrading the reliability.
Conventionally, the dew condensation has been prevented by suppressing an increase in humidity with the use of a desiccant such as silica gel or activated carbon. Such prevention has been satisfactory for magnetic disk drives used indoor.
Demand for the magnetic disk drive is being increased since the magnetic disk drive is incorporated not only into personal computers (PCs) equipped in offices but also outdoors as being incorporated into notebook type PCs and car navigation systems mounted on vehicles. As a result, the use environment of the magnetic disk drive is becoming more severe. In the case where transport of the magnetic disk drives is facilitated, other problems occur, such as an increase in vibration applied on the magnetic disk drives, temperature changes due to environmental changes and humidity changes caused by the temperature changes, and continuous operation under severe environment.
A sharp temperature change in external environment of the magnetic disk drive greatly influences the internal environment of the magnetic disk drive. For instance, when the magnetic disk drive is carried from outdoor to an air-conditioned cool room in summer, the sharp decrease in temperature of the external environment causes a magnetic disk drive internal temperature to decrease sharply. As a result, humidity inside the magnetic disk drive is increased to cause the dew condensation. Since the sharp temperature change hardly occurs under the conventional use environment such as in offices and the like, an increase in humidity caused by a temperature decrease inside the magnetic disk drive under the conventional use environment has been satisfactorily suppressed by the desiccant such as silica gel without a problem. However, the conventional desiccants such as silica gel cannot cope with the sharp increase in humidity; nor can it prevent the dew condensation.
Accordingly, as countermeasures for the dew condensation due to the sharp increase in humidity, the following proposals have been made. Patent Literature 1 (JP-A-8-45263) discloses a technique of disposing metal fibers having a high thermal conductivity in a magnetic disk container as a moisture absorbing structure. With this technique, in the case where an ambient temperature decreases sharply, the temperature of the high thermal conductivity metal fibers is decreased, so that vapor adheres on the surfaces of the metal fibers in the same manner as dew condensation, whereby the metal fibers absorb the vapor inside the container. Patent Literature 2 (JP-A-2002-109855) discloses a technique where a humidity conditioning plate made from a porous material is attached to an inner wall of a housing to cause dew condensation forcibly on the porous humidity conditioning plate, thereby preventing the dew condensation on other components. This technique takes advantage of the fact that the external temperature is lower than the internal temperature. With the technique, a temperature of the humidity conditioning plate is decreased by the external temperature to cause dew condensation on the humidity conditioning plate having the lowest temperature in the internal environment prior to other components, thereby preventing dew condensation on the other components. Patent Literature 3 (JP-A-2003-340233) discloses a technique wherein the capillarity of a porous material is utilized for causing dew condensation, which occurs when a humidity is increased sharply, primarily on the porous material, thereby preventing dew condensation on the other components.